This invention relates to spreader rolls.
In the spreader roll according to the invention a shell made of composite material is used. Due to the advantageous material properties of the composite roll, such as the elastic modulus and density, the composite roll can be dimensioned in such a way that it is bendable to a desired curvature using moderate torque and that it operates either at a subcritical speed, i.e. below the lowest resonance frequency, or between the resonance frequencies. If it is desired to bend a steel roll to the required curvature without the stresses growing excessive, the roll diameter must be very small. In this case exceeding one or more of the roll's critical speeds is unavoidable.
Additionally, for a steel roll the bending moment required by bending is notably higher than for a composite roll, in which case the bearing forces of the steel roll are also notably higher than those of the composite roll.
FI patent 106741 proposes one bendable-material roll for a web-like material. The roll comprises a continuous tube like roll shell made of composite material and journals attached to both ends of the roll shell and rotating with the roll shell. The journals are supported at least with two bearing elements, placed at a distance of each other in the axial direction of the roll, to a support element surrounding the journal, which in turn is supported to the machine frames. The first bearing element is supported to the support element via a bending mechanism, which directs a force affecting in the radial direction to the first bearing element for deviating the first bearing element relative to the center axis of the non-bent roll, whereupon the journal bends relative to the fulcrum created at the second bearing element, and a bending moment is directed to the roll shell. Using such a solution the roll shell can be made to bend to a uniform curvature. However, the solution is not very well suitable for the press section, in which the forces directed to the spreader roll are high.
FI patent 106277 proposes a sectional roll, which comprises several successively located roll components, of which each is mounted with bearings to rotate supported by a support shaft of its own. Arranged on both axial end surfaces of the support shaft of the roll components there are connection elements, such as e.g. a projection and a corresponding recess, by means of which the two successive roll components can be connected to each other in a disconnectable way. The support shaft is composed of at least two parts, the mutual position of which can be changed to modify the axial length of the support shaft to such an extent that the connecting elements on the end surfaces of the two successive sectional rolls contact each other or disengage from the coupling. This enables the replacement of an individual roll component at the center of the sectional roll without the need for dismantling the entire roll assembly. Each roll component is made of two nested cylindrical sleeves, which are connected together by a neck placed symmetrically at their midpoint. The outer cylinder forms the shell of the roll component and the inner cylinder is shorter than the outer cylinder. The inner cylinder is mounted with two bearings by its outer surface to the non-rotating support shaft of the roll component. The support shaft is composed of two flange-like parts, which are connected together by a pin extending through the inner cylinder. The cylinders are rotating while the support shaft is fixed. The other part of the support shaft is supported at its end to a support beam external to the roll component. This support can be adjustable in which case it is possible to adjust the position of an individual roll component relative to the adjacent roll components. Such an arrangement provides the adjustment of the sectional roll curvature. The curvature of a sectional roll is created by the fact that the center axes of the individual roll components are not aligned. The shells of the individual roll components, however, are parallel, whereupon the curvature of the sectional roll forms a fraction line. A sectional roll requires a great number of bearings, which are grease lubricated. The sealing between the support shaft and the shell is also a problem of some degree.